Method of isomerizing and demethanating c-c u-paraffins



July 31, 1962 Filed Dec.

c PRODUCTION RATE, MOLES/HR/ CATALYST x 10 N. CARR 3,047,491

METHOD OF ISOMERIZING AND DEMETHANATING 0 -0 n-PARAFFINS 25, 1957 sSheets-Sheet 2 825'-875 AT 22 mm.

OVER-ALL ACTIVITY DECLINES IN THIS TIME RANGE 5 IO 20 3O 4O 50 I00TREATMENT TIME (HOURS) (IN H AFTER l6 HR. DRY REDUCTION) FIG. 3

INVENTOR.

-\ NORMAN L. CARR ATTORNEY July 31', 1962 N. L. CARR 3,047,491

METHOD OF ISOMERIZING AND DEMETI-IANATING C -C n-PARAFFINS Filed Dec.23, 1957 s Sheets-Sheet s PREFERRED TIME RANGE AT THESE COND 8' X-BUTANE PRODUCTION RATE 0- ISO- PENTANE 0 IO 20 3O 4O 5O 60 TIME INCONTACT WITH CONDITIONING HYDROGEN (HOURS) FIG. 4

INVENTOR.

ATTORNEY 3,047,491 Patented July 31, 1962 3,047,491 METHOD 6F EUMERIZENGAND DEMETHA- NATKNG (C -Q n-PARAFFHNS Norman L. Carr, Crystal Lake, llh,assignor to The Pure Qil Company, Qhicago, Ill., a corporation of OhioFiled Dec. 23, 1957, Ser. No. 704,615 3 Claims. (Cl. 268-136) Thisinvention relates to the isomerization of isomerizable C C hydrocarbons.It is more specifically directed to the upgrading of light petroleumnaphthas containing predominantly straight-chain paraffin hydrocarbonsfor the production of high-octane-number blending stocks.

In the production of gasoline-type motor fuels, a number of processesare employed in an integrated refining operation for the production ofvarious blending stocks which are formulated into a finished gasoline.The normally liquid virgin distillates boiling within the range of100-400 F. have either been used per se or subjected to thermal orcatalytic reforming, or hydroforming, to produce blending stocks ofimproved octane numbers. It is preferred, however, in preparing feedstocks for use in reforming or hydroforming operations, to use theheavier fractions boiling within the gasoline range because thelow-boiling fractions containing predominantly C C straight-chainparaffinic hydrocarbons are not receptive to reforming. Due to thedemand for highoctane, gasoline-type motor fuels needed by increasinglypowerful internal combustion engines, isomerization has become importantas the best method for raising the octane level of the straight-chainparatfinic C C hydrocarbons. Accordingly, the increased performancerequirements of gasoline have become the basis for the extensivecommercial application of isomerization.

Although the isomerization reaction predominates in a catalyticisomerization process, disproportionation and cracking side-reactionsare of such a magnitude that prac tical commercial utilization of theisomerization process is hindered. The problem of hydrocracking anddisproportionation becomes especially serious when isomerizable,saturated hydrocarbons of higher molecular weight are processed in thepresence of isomerization catalysts which are effective at temperaturesWithin the range of GUN-800 F. Another problem relating to the molecularWeight of the isomerization feed stock is the difliculty which isexperienced in forming gem-substituted C and C parafiinic hydrocarbons.These types of isomerization reaction products are preferred because thehighly branched forms of hydrocarbons provide marked increases in octanenumber.

Isomerization is a reversible reaction the rate of which can beconsiderably influenced by the presence of catalytic agent. Althoughearlier investigators of the isomerization reaction employedFriedel-Crafts-type catalysts, more recent development work in thisfield has been carried out employing solid catalysts. It has been foundthat catalysts compositions comprising a major portion of a refractory,mixed oxides base, composited to evince acidic properties andhydrocarbon cracking activity, and a small amount of a hydrogenationagent are effective for promoting the efficiency of the isomerizationreaction. (Vide Isomerization of Saturated Hydrocarbons in the Presenceof Hydrogenation-Cracking Catalysts, Ciapetta, et 211., Industrial andEngineering Chemistry, 45, 147 et seq.) Specific catalysts are preparedby incorporating a small amount of a hydrogenation agent in arefractory, mixed oxides base. Specific hydrogenation agents include theelemental group IV or group VIII metals, such as iron, platinum, cobalt,and nickel, their oxides, and their salts, including molybdates,tungstates, chromates, and borates, as Well as the oxides of chromium,molybdenum and tungsten, alone or in admixture. Because they aresusceptible to permanent loss of activity with continued use, extensivework has been carried out to improve the activity and life of thesecatalysts by specific preconditioning treatments. In U.S. patentapplication Serial No. 619,376, filed October 31, 1956, now [1.8. PatentNo. 2,917,565, there is described a multiple-step preconditioningprocess employing a sequential oxidation and reduction treatment.Essentially, this preconditioning process involves a two-partmanipulative technique, viz., (a) the catalyst preparation carried outin accordance with the prior art, and (b) the preconditioning process ofoxidizing and reducing which was found to be exceptionally anddistinctively effective for inducing high activity and stability byimparting resistance to permanent depreciation in activity. Although theoverall effect of this catalyst preconditioning method has been toprovide a stable catalyst which is useful in improving the octane numberrating of feed stocks boiling Within the gasoline range, investigationof the reaction products has shown that the method increased thepropensity of the catalyst to promote undesired near-middlehydrocracking of the individual paraffinic constituent molecules asdistinguished from desired demethylation. In specific instances, therate of isopentane hydrocracking is increased in absolute magnitude aswell as relative to normal pentane hydrocracking.

It is, therefore, the primary object of this invention to provide acatalyst conditioning method which will modify the catalytic propertiesof an isomerization catalyst, composed of a refractory, mixed oxidesbase composited to evince acidic properties and hydrocarbon crackingactivity, and a small amount of a hydrogenation agent, to enhance theeffectiveness of the catalyst composition in promoting isomerizationreactions as its principal activity, and in preferentially promotingdemethylation reactions as its secondary activity. It is another objectof this invention to provide a conditioned isomerization catalyst toaccelerate the isomerization of saturated hydrocarbons at temperaturesWithin the range of about 600-800 F. Still another object of thisinvention is to provide a conditioned solid isomerization catalyst whicheffectively promotes the isomerization and selective demethylation offeed stocks consisting of saturated hydrocarbons having 58 carbon atomsper molecule. These and other objects will become more apparent from thefollowing detailed description of this invention, and accompanyingdrawing, of which:

FIGURE 1 is a flow diagram of a typical isomerization process employingthe principles of this invention;

FIGURE 2 is a flow sheet diagramming the process steps employed inpreparing the conditioned catalysts of this invention;

FIGURE 3 is a graphical presentation of the critical conditions of thisinvention; and

FIGURE 4 is a graphical illustration of the effect of time of treatmenton isomerization and methylation under specified conditions.

According to this invention, the utility of isomerization processesinvolving the treating of C C hydrocarbons is enhanced by employing asolid catalyst which is conditioned in such a manner as to promoteisomerization, as the principal reaction, and preferentially promotedemethylation, as a subordinate but' concomitant reaction. The catalystwhich is conditioned in accordance with this invention is a solidcomprising a major amount of mixed oxides base, composited to evinceacidic properties and hydrocarbon cracking activity, and a minor amountof a hydrogenation agent. The catalysts susceptible to conditioningaccording to this invention are prepared by conventional techniques andcommonly are activated by methods wherein the final activation stepinvolves subjecting the composition to a reducing step which reduces thereducible constituents of the composition to their lowest state ofvalency attainable at the reducing conditions imposed. The catalyst inthis conditionis effective for producing motor fuel components ofincreased octane numbers, but its use in this form gives rise to certaindisadvantages. Conditioning the catalyst before use according to thisinvention significantly mitigates these disadvantages. Similarly,catalysts of this kind which have become degenerated during use inhydrocarbon processing, when regenerated by conventional techniques alsoare effective in promoting reactions which yield products of increasedoctane numbers, but they possess similar disadvantages. The conditioningmethod of this invention is also effective in improving these catalysts.

In general, the hydrogenation agents employed in the catalysts definedabove fall into the distinct categories of base and noble metals.Notable among useful basemetal-containing isomerization catalysts arethose in which nic (e1, or nickel in combination with molybdena, is thehydrogenation agent. Among the noble-metal-containing isomerizationcatalysts are those in which palladium or platinum is the hydrogenationagent. In its broadest aspect, this invention is based upon my discoverythat catalysts containing either of these types of hydrogenation agentcan be conditioned to provide a unique process in which isomerizable C-C hydrocarbons are converted to more valuable products throughpredominantly isomerization and demethylation reactions. However, I alsohave discovered that different techniques are required to condition eachof these types of catalysts for the attainment of desired activity andspecificity of reaction-promoting propensity. I have discovered furtherthat the attainment of these characteristics in base-metalcontainingcatalysts is critically dependent upon the manner in which thecatalysts, in reduced condition, are subjected to treatment with amoistureand hydrogen-containing gas. On the other hand, the attainmentof this characteristic in noble-metal-containing catalysts is criticallydependent upon the manner in which the catalyst is subjected to a firsttreatment with moisture-and oxygencontaining gas and a second treatmentwith a dry, hydrogen-containing gas.

Specifically, the method which I have found to be uniquely effective inconditioning a base-metal-containing catalyst requires thatsubstantially all of the catalyst constituents first be at their higheststate of oxidation, and that the catalyst be free of contaminants andmoisture. Thus, freshly-prepared, virgin catalysts, which commonly arepelleted and dried after compounding, are susceptible to conditioningWithout further pretreatment. Catalysts which have become degenerated byprevious use in processing hydrocarbons must be first subjected tooxidation. I have found that satisfactory oxidation can be accomplishedby contacting the catalyst with a dry mixture of inert gas and oxygen,containing oxygen at a partial pressure of 30-500 mm. Hg, at atemperature of 800-875 F. for a time suflicient to oxidize carbonaceousdeposits on the catalyst and the oxidizable constituents of the catalystcomposition. The oxygen-containing gas preferably is dry, but maycontain Water vapor at a partial pressure up to about 10 mm. Hg Withoutserious deleterious effect.

The resulting base-metal-containing catalyst, in oxidized state, issubjected to a conditioning method which consists of the followingsequential steps: (1) Purge.0xygen and combustion products are removedfrom the catalyst bed by purging With inert gas, or by evacuation to alow absolute pressure in the range of 10 mm. Hg.

(2) Reducli0n.-The reducible constituents of the composition then arereduced in a three-stage sequence wherein (a) The oxidized catalyst iscontacted with a flowing stream of substantially dry,hydrogen-containing gas at a temperature of about 600-975 F. for aperiod suflicient 4- to remove water, generated by the reductionreaction, from the catalyst bed;

(17) The catalyst is contacted further with dry hydrogen, either bycontinuing flow or shutting in the catalyst for 15-30 hours Whiletemperature is maintained at 900-975 F, and pressure at 0-600 p.s.i.g.;

(c) The reduced catalyst then is contacted with flowing, moistureandhydrogen-containing gas at a temperature of about 800-975 F. for aperiod of about 5-50 hours. The gas should contain Water equivalent to apartial pressure in mm. of Hg of about 15-100 and preferably 20-30.

The method which I have found to be effective in conditioningnoble-metal-containing catalysts consists of the following sequentialsteps:

(1) Purge-The catalyst bed is purged with an inert gas for a timesufiicient to displace gaseous hydrocarbons and/or hydrogen therefrom.

(2) Oxidati0n.-The catalyst is contacted with an oxygen-containing inertgas, containing oxygen at a partial pressure of 10-500 mm. Hg and watervapor at a partial pressure of 0-90 mm. Hg, at a temperature of 825-975"F. for 1-20 hours. Temperature, Water-vapor partial pressure, and lengthof treatment are critically interrelated in this step. At an oxidationtemperature of 825 F, the water-vapor partial pressure must be in therange of 20-90 mm. Hg and the length of treatment must be about 20hours. At an oxidation temperature of 975 F., the water-vapor partialpressure must be in the range of 0-15 mm. Hg, and the length oftreatment must be limited to about 1 hour.

(3) Purge.Oxygen, combustion products, and moisture then are removedfrom the catalyst bed by purging With inert gas, or by evacuation to asubatmospheric pressure in the range of 10 mm. Hg, absolute.

(4) Reduction-The reducible constituents of the oxidized catalystcomposition then are reduced to the greatest extent possible by passinga stream of dry, hydrogencontaining gas through the catalyst bed forl-30 hours at a temperature of 850-950 F. and a pressure of 15- 750p.s.i.g. While dry gas is preferred, water-vapor partial pressures ashigh as 10 mm. Hg can be employed without serious deleterious effect.

In carrying out a catalyst preparation in accordance with thisinvention, the preconditioning steps may be carried out in a separateprocessing system, or an active catalyst prepared in accordance with theprior art can be disposed in the isomerization reactor and thepreconditioning carried out as a preliminary to introducing theisomerization feed into the reaction system. This latter method ofpreconditioning is preferred in order to avoid changes in catalystcomposition which may inadvertently occur in handling the preconditionedcatalyst prior to its being placed in the reaction system.

Catalysts which may be preconditioned in accordance with this inventionare composite compositions comprising a refractory, mixed oxides basecomposited to evince acidic property and hydrocarbon cracking activity,having incorporated therein a small amount, i.e., 0.1 to about 10% of ahydrogenation agent. Specific examples of the refractory, mixed oxidesbase include but are not limited to silica-alumin, silica-zirconia,silicatitania, silica-boria, alumina-zirconia, alumina beryllia,alumina-boria, silica-chromia, boria-titania, silica-alumina-zirconia,silica-alumina-beryllia, and acid-treated clays. The hydrogenation agentwhich is employed can be a group VIII metal, oxide of a poiyvalent metalof group V, VI and VII, or group VIII, metal, and metal salts of theoxyacids of polyvalent metals of groups V, VI and VII. Specific examplesof suitable hydrogenation agents, include but are not limited to cobalt,nickel, platinum, tungsten oxide, molybdenum oxide, chromium oxide,manganese oxide and vanadium oxide; and cobalt, nickel and platinumsalts of the oxyacids of tungsten, molybdenum, chromium, vanadium ormanganese, e. nickel tungstate, cobalt molybdate, nickel molybdate. Ithas been found that silica-alumina catalyst carriers containing 50-87%silica and 5013% alumina, having incorporated therein 02 to of thehydrogenation agent, particularly nickel, nickel molybdate, palladium orplati' num, have superior activities and are preferred.

This invention, as applied to a base-metal-containing catalyst, wasdemonstrated by experiments in which catalyst compositions containing2.7% wt. nickel and 4.7% wt. molybdenum (present as molybdena) as thehydrogenation agent, on a support consisting of 75% wt. silica and 25%wt. alumina (a conventional, commercial cracking catalyst) were used.Such catalysts can be prepared as follows:

A solution of 32 grams of ammonium heptamolybdate and 20 cc. ofconcentrated ammonium hydroxide in 270 ml. of distilled water is heatedto 176 F. To this solution, with stirring, is added 58.7 grams of nickelnitrate in 270 ml. of water. After dissolution, 360 grams of commercialfluid cracking catalyst, containing 75% wt. silica and 25% wt. alumina,are added. The mixture is stirred for about minutes, after which theimpregnated solid material is filtered from the supernatant liquid andwashed with five 670 ml. portions of distilled water. The catalyst cakethen is dried for 16 hours at 230 F. and pelleted.

In one series of experiments, virgin catalysts were subjected toconditioning according to my method, as follows:

EXAMPLE I A batch of freshly-prepared, pelleted, dried catalyst wasplaced in the reaction vessel of a pilot-plant unit for evaluatingcatalysts and process variables, and was slowly heated in a flowingstream of dry hydrogen to a temperature of 975 F, at which temperatureit was held for 29 hours while continuing the how of hydrogen. Then thecatalyst temperature was lowered to 825 F, and water vapor was added tothe hydrogen to bring its vapor pressure to 22 mm. Hg. This conditionwas maintained for hours, after which the catalyst bed was cooledfurther to 705 F. for an isomerization processing test. The test wasconducted using normal pentane as the feed stock, with dry hydrogenbeing added at a hydrogen/hydrocarbon mol ration of 1/ 1. Hydrocarbonspace velocity was 2.8 v./hr./v. Pentane conversion was 50.7 molpercent, isopentane yield was 45.9 mol percent, and n-pentane-isopentaneselectivity was 90.6%. Adjusted to operation at a space velocity of 3.3vol./hr./vol., conversion was 45.9 mol percent, and isopentane yield41.1 mol percent. In this experimental test, the rate of butaneproduction was 9.6 10 g.-mole/ hr./ g. catalyst. The amount of butaneand methane formed by demethylation exceeded the amount of ethane andpropane formed through middlemolecule cracking by 360%.

When a similar catalyst composition, which had been activated 'byoxidation and reduction according to conventional practice, was testedat these same conditions, the test had to be terminated soon afterprocessing was initiated because hydrocracking, which is highlyexothermic, was so great that catalyst temperatures rapidly anduncontrollably increased.

EXAMPLE II The used catalyst of Example I was regenerated, after beingpurged free of gaseous hydrocarbons and hydrogen by flowing nitrogenthrough it. While continuing nitrogen flow, the catalyst was cooled toabout 700 E, whereupon a small amount of air was added to the nitrogento burn carbonaceous deposits and other contaminants from the catalystsurfaces. Burning was evidenced by a rise in temperature at theso-called flame-front which progressed through the catalyst bed from theinlet and to the exit end. When no further evidence of temperature risewas noted, indicating that burning had been completed, the catalyst bedwas heated to about 975 F. and dry air,

same as given in Example III.

without dilution, was passed through the system for about one hour toassure completion of oxidation.

The system then was again purged with nitrogen and the catalyst wasreduced by being contacted at 975 F. with flowing dry hydrogen for aperiod of about 24 hours. After being reduced, the catalyst wasconditioned by being contacted with wet hydrogen, containing water vaporat a partial pressure of 30 mm. (Hg), at 875 F. for 18 hours. Theconditioned catalyst then was used in an isomerization test whereinnormal pentane and hydrogen, at a hydrogen/pentane mol ratio of 1, werepassed through the catalyst bed at a pentane space velocity of 3.3vo1./hr./vol. of catalyst. Catalyst temperature was 702 F., and pressurewas 500 p.s.i.g.

In this test, n-pentane conversion was 43.8 mol. percent, isopentaneyield was 40.4 mol percent, and n-pentane-toisopentane selectivity was92.2%. The rate of butane production was 7.6 10 gm.-mole/ hr./ gram ofcatalyst, and the amount of butane and methane formed by demethylationcracking exceeded the amount of ethane and propane formed throughmiddle-molecule cracking by When a similar catalyst is regenerated andreactivated by conventional methods in which reduction is achieved withdry hydrogen, the resulting catalyst is so hot, i.e., the extent ofexothermic hydrocracking is so great, that the catalyst cannot be used.Uncontrollable temperature increases occur in the catalyst bed.

EXAMPLE III A second batch of freshly prepared and pelleted catalyst,having the same composition, was conditioned as in Example I, exceptthat the conditioning was at 825 'F. for 50 hours with hydrogencontaining water vapor at a partial pressure of 22 mm. (Hg). In testingthe catalyst with normal pentane as the feed, space velocity was 3.3v./hr./v., hydrogen/hydrocarbon mole ratio was 1, and catalysttemperature was 702 F.

In this test, pentane conversion was 41.0 mol percent, isopentane yieldwas 37.8 mol percent, and selectivity was 92.3%. Butane production ratewas 7.9, 10 gm.- mole/ hr./ gram of catalyst, and the amount of butaneand methane produced was 520% greater than the amount of propane andethane.

EXAMPLE IV The used catalyst of Example III was regenerated andconditioned by the method of Example II, except that the conditioningwith wet hydrogen consisted of two steps. In the first step the catalystwas contacted with hydrogen containing water vapor at a partial pressureof 22 mm. (Hg) at 975 F. for 16 hours. In the second step the cat alystwas contacted with hydrogen containing water vapor at a partial pressureof 22 mm. (Hg) at 800 F. for 3 hours. In the isomerization test, normalpentane and hydrogen, at a hydrogen/pentane mole ratio of 1, were passedthrough the catalyst bed at a pentane space velocity of 3.3vo1./hr./vol. of catalyst. Catalyst temperature was 702 F. and pressurewas maintained at 500 p.s.i.g. Normal pentane conversion was 41.7 molpercent, isopentane yield was 39.2 mol percent, and selectivity was 93.9percent. Butane production rate was 5.6 10 gm.-mole/ hr./ gram catalystand butane-methane production exceeded ethane-propane production by150%.

EXAMPLE V Another portion of freshly-prepared and pelleted catalyst,having the same composition, was conditioned as in Examples I and III,except that the conditioning was conducted for 20 hours at 875 F., usinghydrogen which contained water vapor at a partial pressure of 22 mm.(Hg). Isomerization test conditions were essentially the Pentaneconversion was 43.7 mol percent, isopentane yield was 39.9%. Butaneproduction rate was 10.1 10 gm.-mole/hr./gram of 7 catalyst, andbutane-methane production exceeded propane-ethane production by 440%.

EXAMPLE VI Example V was repeated with another portion of catalyst,except that the conditioning consisted of contacting the catalyst at 825F. for five hours with hydrogen which contained water vapor at a partialpressure of 23 mm. (Hg). Test conditions were similar to those ofExample III. Normal pentane conversion was 45.5 mol percent, isopentaneyield was 36.9 mol percent, and selectivity was 81.1%. Butane productionrate was 27 1O gm.-mole/ hr./ gram of catalyst, and butane-methaneproduction exceeded ethane-propane production by 610%.

EXAMPLE VII In another experiment, a portion of catalyst having thecomposition of the catalysts used in Examples IVl was conditioned bybeing contacted at 900 F. with hydrogen which contained water vapor at apartial pressure of 22 mm. (Hg). Contact was maintained for hours. In atest run at 648 F., and 500 p.s.i.g., normal heptane was isomerized overthis catalyst at a space velocity of 1.1 vol./hr./vol., with a hydrogen/hydrocarbon mol ratio of 1.2. Normal heptane conversion was 76.7 molpercent, isoheptane yield was 49.3 mol percent, and hexane yield was14.7 mol percent. Thus, it can be seen that this conditioned catalystwas active in promoting isomerization and demethylation.

For greater clarity, the results of these experiments are listed inTable I. The critical interrelationship of the effects of temperature,length of time, and water vapor partial pressure on butane productionrate are shown in FIG- URE 3. The effects of these variables onisopentane yield and demethylation are shown graphically in FIGURE 4. Itcan be seen that when the catalyst is conditioned by contact withhydrogen-containing water vapor at a partial pressure of 22 mm. (Hg) at825 F., the length of time of contact has a profound effect onisopentane yield and demethylation.

of solution used being compatible with the absorptive capacity of thesupport. Hydrochloric acid is necessary to keep the palladium salt insolution at room temperature in the concentrations required.Alternatively, heating to about 180 F. will keep the palladium salt insolution. After having been dried and pelleted, the green catalysts aredecomposed, i.e., the palladium chloride is decomposed and reduced tometallic palladium by contact with hydrogen at an elevated temperature.Following this decomposition step, the catalysts conventionally areactivated by oxidation followed by reduction at elevated temperatures.The catalysts are regenerated after use by again being oxidized andreduced at elevated temperatures, the oxidizing step being employedprimarily to burn carbonaceous and other contaminating deposits from thecatalyst. I have found that the isomerization and demethylationpropensities of such catalysts are critically dependent upon theconditions to which the catalyst is subjected in these oxidizing steps.

The demonstration experiments were as follows:

EXAMPLE VIII A previously-used, degenerated portion of the describedcatalyst was oxidized at 850 F. by passing nitrogen, containing oxygenat a partial pressure of 35 mm. (Hg) and water vapor at a partialpressure of 90 mm. (Hg), through the catalyst bed for one hour. Then thebed was purged free of oxygen by passing nitrogen through it, and thecatalyst was reduced at 850 F. by passing hydrogen containing watervapor at a partial pressure of 90 mm. (Hg) through the bed for hours.

An attempt was then made to use the catalyst in the isomerization ofnormal pentane, in the presence of hydrogen at a hydrogen/hydrocarbonmol ratio of 1.7, at 750 F., 395 p.s.i.g., and at a pentane spacevelocity of 3.0 vol./hr./vol. of catalyst. The catalyst was so hot,i.e., exothermic hydrocracking reactions caused such a rapiduncontrollable temperature rise, that operation was impossible. Theisopentane yield was only about 6%.

Table I.Is0merizati0n and Demethylation of Pentane Over a Base Mearl-Containing Catalyst Example 1 2 3 4 Treatment Conditions inhydrolime, hr 20 18 50 16 Ternp., 825 875 825 975 H1O partial pressuremm.

Hg 22 30 22 22 Run Conditions:

mp., F 705 702 IEU/HC mol ratio. 1 LV V 2.8 3.3 Pressure, p.s.i.g 500500 Results:

nC Conv., mol percent 50. 7 45. 9) 43.8 i-O Yield, mol percent 45. 9(41.1) 40. 4 Selectivity, percent 90.6 04 Production Rate, g.m01/hr./g.

cat. 10 9.6 M01 ratio: (0 +6 4 6 2 5 6.2 (o3+o2) 2 5 Percent more(CH-C1) formed than (02+03), (mole basis) 360 150 520 150 1 Corrected toLVHSV=3.3.

r a freshly dried support with a solution of palladium chlo- EXAMPLE IXThe hot catalyst of Example VIII then was subjected to oxidizingconditions at 850 F., after having been evacuated to about 10 mm. Hg,absolute to remove water, by passing a dry air-nitrogen mixture throughthe bed for 1 hour. After oxidation, the catalyst bed was againevacuated for 15 minutes, and was then subjected to reduction at 850 F.by passing dry hydrogen through it for 1.5 hours.

After this treatment, the catalyst was again used in isomride in aboutone-normal hydrochloric acid, the volume erizing normal pentane at thesame conditions employed in Example VIII. Normal pentane conversion was28.4 mol percent, isopentane yield was 21.1 mol percent, and butane andlighter yield was 7.3 mol percent. The catalyst had been made operableby this treatment, but its activity was uneconomically low.

EXAMPLE X The catalyst of Example IX then was subjected to the method ofthis inventon, in which it was oxidized at 850 F. by passing nitrogen,containing oxygen at a partial pressure of 35 mm. (Hg) and water vaporat a partial pressure of 15 mm. (Hg), through the bed for 1 hour. Then,after being purged with nitrogen, the catalyst was reduced by contactwith dry hydrogen at 850 F. for 1 hour. When the catalyst was employedin the isomerization of normal pentane at the conditions of the previousexamples, normal pentane conversion was 62 mol percent, isopentane yieldwas 45 mol percent, butane yield was 11.5 mol percent, and propane andlighter yield was only 4.5 mol percent. Thus, my method had rendered thecatalyst very active, reasonably selective in promoting isomerization asthe primary reaction, and very selective in promoting demethylation asthe predominant side reaction.

To employ the preconditioned catalyst prepared in accordance with thisinvention in an isomerization process, a suitable isomerization feedstock is processed in a reaction system employing operating conditionswithin the following range:

While the isomerization process employing the preconditioned catalyst ofthis invention can be utilized as a separate unit in the processing ofselected isomerization feed stocks, it is preferred that the process beemployed in an integrated refining operation wherein the primaryobjective is the upgrading in-octane number of light petroleumdistillates boiling in the gasoline range. In this instance, in order toimprove the octane number of a full-boiling-range gasoline, theisomerization process can be employed in conjunction with a reformingoperation. In this operation the full-boiling-range gasoline isinitially fractionated to produce a low-boiling range fraction and ahigh-boiling-range fraction. The low-boiling-range fraction, having aboiling range of about 100250 F. and consisting predominantly ofstraight-chain paraifinic hydrocarbons, is contacted in an isomerizationprocess employing the preconditioned catalyst of this invention. Thehigher-boiling fraction is thereafter processed in a catalytic reformingor hydroforming process which aromatizes and cyclizes the constituentsof the higher-boiling range fraction. The reformate from the reformingstep is then treated in a refining operation, such as solventextraction, to remove the aromatic constituents which were produced inthe reforming operation. The paraflinic constituents of the reformatewhich are produced in the course of the reforming operation are thenrecycled for subsequent processing in the isomerization zone of thecombination, isomerization-reforming, integrated unit. If preferred, itmay also be desirable to utilize a plurality of isomerization zonescontaining catalysts and operating under reaction conditions which areconducive to the processing of separate feed stocks at maximumefliciency. In other words, the low-boiling fraction boiling within thegasoline range may be further fractionated to produce separate cutswhich are rich in C C C or C paraffinic hydrocarbon constituents. Theseparate streams can then be fractionated in separate reaction systemswhich are operated under conditions which will provide optimum effectwith regard to upgrading in the octane number of the selected feedstocks. It is apparent that other manipulative techniques may beutilized in carrying out the instant invention, which is directedprimarily to a preconditioned catalyst and process for the isomerizationof C C saturated hydrocarbons.

In carrying out an isomerization process of this nature, low-boiling,saturated, hydrocarbon-containing feed stocks are employed. Such stocksinclude normal paraffins containing not more than about 8 carbon atomsper molecule, or naphthenic hydrocarbons, as well as mixtures of thesehydrocarbons which are found in straight-run, light, petroleumdistillates boiling between about 250 F. Such light petroleumdistillates include straight-run gasolines which are obtained in thefractionation of crude petroleum oil, as well as natural gasoline. Incarrying out the isomerization process, conventional contact equipmentand product recovery systems can be employed. A typical installation isshown in FIGURE 1. A light naphtha distillate rich in saturatedhydrocarbons is passed via lines 10 to heating coil 11. Hydrogenadmitted to the system through line 12 is then mixed with the naphthafeed and the combined feed is heated to reaction temperature in coil 11before being introduced into the reactor 15, which contains catalystpreconditioned in the manner previously described. The reaction efiluentleaves reactor 15 through line 16 and is sent to a highpressureseparator 17 to effect a separation of the liquid isomers, which aredischarged from the reaction system through line 18, from the oif-gas,which leaves separator 17 by means of line 19 and is sent to knockoutdrum 20 wherein any entrained isomerization liquid is recovered. Thegaseous efliuent is withdrawn to line 21. Because this efliuent is richin hydrogen, provision is made for recycling a portion of this gas tothe reactor by means of line 22 which interconnects with the hydrogenfeed line 12. The gas which is not used for the recycle operation ispassed via line 23 to an absorbing section (not shown), where anyremaining hydrocarbon fractions boiling in the gasoline range arerecovered.

During the isomerization reaction the proconditioned catalyst of thisinvention may become contaminated with various materials which lower itscatalytic activity. When the activity falls below the desired level itis regenerated in the manner previously described, and as illustrated inFIGURE 2.

FIGURE 3 graphically shows the effect of time, tem perature and waterpartial pressure during hydrogen conditioning on rate of demethylation.With increase in time, demethylation rate decreases rapidly and thenlevels off, whereas isomerization selectivity and activity increases toa maximum and then falls off slowly. For short conditioning periods theactivity of the catalyst is high, but the isomerization selectivity ofthe catalyst is low and demethylation selectivity is high. Increase inmoisture content of the conditioning hydrogen also decreases thedemethylation rate. Therefore, if the object is to promote isomerizationwith minimum amount of demethylation, the catalyst s hould beconditioned with Water vapor pressures above 20 mm. of Hg, and the timeof conditioning should be at least 15 hours. On the other hand, if it isdesired to promote demethylation together with isomerization, as forexample, in the processing of heptane-rich stock, the conditioning timeshould be short and preferably at the lower temperature range, asdemonstrated by Example 6 and the graphs in FIGURE 3.

FIGURE 4 shows the preferred time range for conditioning a catalyst at825 F. with hydrogen containing water at 22 mm. of Hg partial pressurein order to obtain maximum isomerization selectivity and activity. Below10 hours, isomerization selectivity and yield fall oif sharply.Conditioning times above 20 hours adversely affect isomerization yieldwithout having any material effect on demethylation.

Although the invention has been described as being particularlyadaptable to use in connection with a reaoazam forming operation, it canbe employed in conjunction with other types of refining processes inorder to provide an integrated refining operation for the upgrading ofpetroleum distillate stocks to produce a finished gasoline having a highoctane number rating. It is, therefore, intended that the followinginvention be limited only in the manner described in the appendedclaims.

This application is a continuation-impart of my copending patentapplications, now United States Patents 2,917,565 and 2,917,566, havingefiective filing dates of December 8, 1955.

What is claimed as my invention is:

1. A method of isomerizing and demethan-ating C -C n-paraflins whichcomprises passing a mixture of hydrogen and C -C parafiins in ahydrogen/hydrocarbon mol ratio of 0.5-6.0/1, at a pressure of 50-1000p.s.i.g., and temperature of 600-800 F., over an isomen'zation catalystconsisting essentially of a promoter selected from the group consistingof nickel, reduced nickel molybdate,

and reduced nickel phosphate supported on an acidic 2O oxidizableconstituents of the catalyst, removing oxygen and combustion productsfrom the catalyst, subjecting the oxidized catalyst to reduction with adried hydrogen at 850-975 F. for a' time, in the range from about 15-30hours, sufiicient to reduce completely all reducible catalystcomponents, followed by contacting the reduced catalyst with hydrogencontaining water vapor at a partial pressure of 15-100 mm. Hg, at atemperature of 800-975 F. for a time, in the range from about 5 to 50hours, sufli- II cient to condition the catalyst so that theisomerization reaction is substantially free of exothermichydrocracking. 2. A method in accordance With claim 1 in which thecatalyst comprises nickel molybdate on silica-alumina.

3. A method in accordance With claim 1 in Which the water partialpressure in the hydrogen treating gas is about 20-30 mm. Hg.

References Cited in the file of this patent UNITED STATES PATENTS2,671,763 Winstrom et al Mar. 9, 1954 2,870,085 Love Jan. 20, 19592,879,232 Malo et al Mar. 24, 1959 2,882,241 Slyngstad et a1 Apr. 14,1959 2,906,697 Hall et al Sept. 29, 1959 2,968,631 Carr et al Jan. 17,1961

1. A METHOD OF ISOMERIZING AND DEMETHANATING C5-C8 N-PARAFFINS WHICHCOMPRISES PASSING A MIXTURE OF HYDROGEN AND C5-C8 PARAFFINS IN AHYDROGEN/HYDROCARBON MOL RATIO OF 0.5-6.0/1, AT A PRESSURE OF 50-1000P.S.I.G., AND TEMPERATURE OF 600*-800*F., OVER AN ISOMERIZATION CATALYSTCONSISTING ESSENTIALLY OF A PROMOTER SELECTED FROM THE GROUP CONSISTINGOF NICKEL, REDUCED NICKEL MOLYBDATE, AND REDUCED NICKEL PHOSPHATESUPPORTED ON AN ACIDIC SILICA-ALUMINA HYDROCARBON CRACKING CATALYST,CONTAINING 50-87% WT. SILICA, SAID CATALYST HAVING BEEN PRECONDITIONEDTO INCREASZE CATALYST ACTIVITY AND SELECTIVITY FOR ISOMERIZATION BYOXIDIZING THE CATALYST WITH A DRY MIXTURE OF AN INERT GAS CONTAININGOXYGEN AT A PARTIAL PRESSURE OF 30-500 MM. HG, AT A TEMPERATURE OF ABOUT800*-875* F., FOR A TIME SUFFICIENT TO COMPLETELY OXIDIZE THE OXIDIZABLECONSTITUENTS OF THE CATALYST, REMOVING OXYGEN AND COMBUSTION PRODUCTSFROM THE CATALST, SUBJECTING THE OXIDIZED CATALYST TO REDUCTION WITH ADRIED HYDORGEN AT 850*-975*F. FOR A TIME, IN THE RANGE FROM ABOUT 15-30HOURS, SUFFICIENT TO REDUCE COMPLETELY ALL RESDUCIBLE CATALYSTCOMPONENTS, FOLLOWED BY CONTACTING THE REDUCED CATALYST WITH HYDROGENCONTAINING WATER VAPOR AT A PARTIAL PRESSURE OF 15-100 MM. HG, AT ATEMPERATURE OF 800*-975* F. FOR A TIME, IN THE RANGE FROM ABOUT 5 TO 50HOURS, SUFFICIENT TO CONDITION THE CATALYST SO THAT THE ISOMERIZATIONREACTION IS SUBSTANTIALLY FREE OF EXOTHERMIC HYDROCRACKING.